Conventional power supply designs intended for redundant applications typically include OR-diodes. An OR-diode is typically utilized in redundant power supply systems at the outputs of parallel connected power supplies to provide higher output power and prevent a dead power supply or a power supply with a low output voltage from drawing current from a power supply with a higher output voltage or vice versa. An OR-diode may refer to a plurality of diodes in which, for a positive output power supply, the cathodes of each diode are connected to a common output of a plurality of redundant power supplies and anodes of each diode are coupled to the individual outputs of the individual power supplies. For a negative output power supply, the anodes of each diode are connected to a common output of a plurality of redundant power supplies and cathodes of each diode are coupled to the individual outputs of the individual power supplies.
A problem associated with the use of OR-diodes arises when inductive loads, such as computer data storage disk drives and fans, are powered by the redundant power supplies. Inductive loads introduce positive voltage spikes on their DC input which reverse polarize the OR-diodes. The output capacitors, connected after the OR-diodes of the redundant power supplies, are typically too small to provide suppression of voltage spikes over the specified maximum voltage of the power supplies caused by inductive loads. As a result, the voltage spikes may cause damage to the electronic control circuits of the inductive loads. Consequently, a method and system for preventing voltage spike feedback of switched inductive loads connected to isolated redundant power supplies is necessary.